FIG. 11 partially illustrates one example of a conventional thermal print head (see, e.g., JP2001-232838A). A thermal print head 90 shown in FIG. 11 includes a partial glaze 91 formed on a substrate (not shown). The partial glaze 91 is made of glass and has an arc-like strip-shaped cross section in a primary scanning direction x. An electrode layer 92 and a resistor layer 93 are formed one above another on the partial glaze 91. Heat needed to perform printing is generated by partially applying an electric current to the resistor layer 93 through the electrode layer 92. The electrode layer 92 and the resistor layer 93 are covered with a protective layer 94. The protective layer 94 is made of, e.g., glass, and is provided to protect the electrode layer 92 and the resistor layer 93.
In recent years, printing speed has been increasing. Along with the diversification of print medium, it is sometimes the case that a print medium containing a relatively hard material is put to use. These types of print medium are major culprits of scratching the protective layer 94. The protective layer 94 is required to be scratch-resistant and needs to have a smooth surface suitable for printing.